simple prestashop task

[login to view URL] this is the website....... Client comments........ then the visitor fills the CART and wants to checkout. But the checkout is like a qoute system. After checking out the cart is saved as a order in the backend, but then the owner must be able to edit this cart/order so change prices, quantity. After that, the owner must be able to send the quote back to the visitor. Then the visitor can accept this and then check out/pay My Understanding................ okay, i got your point now, first time when user logged in into the website they will see the price and can checkout which will just a quote form and once that is completed an notification email will be sent to admin and order will be saved in back-end and in back-end admin will be able to edit the quantity and price for the order they have done from user section once admin update the things in back-end then notification email will be sent to user and if they accept they will be able to make payment on the website.